Film cooling hole including offset diffuser portion

ABSTRACT

A component for a gas turbine engine including a body having at least one internal cooling cavity and a plurality of film cooling holes disposed along a first edge of the body. At least one of the film cooling holes includes a metering section defining an axis, and a diffuser section having a centerline. The centerline of the diffuser section is offset from the axis of the metering section.

CROSS-REFERENCE TO RELATED APPLICATION

This application claims priority to U.S. Provisional Application No.62/258,097 filed Nov. 20, 2015.

TECHNICAL FIELD

The present disclosure relates generally to film cooling holes, andspecifically film cooing holes for gas path components of a gas turbineengine.

BACKGROUND

Gas turbine engine include a compressor for compressing air, a combustorfor mixing the compressed air with a fuel and igniting the mixture, anda turbine across which the resultant combustion products are expanded.As a result of the combustion, temperatures within the turbine enginegas path connecting each of the sections are extremely high. With somecomponents the extreme temperatures require active cooling systems tokeep the components exposed to the gaspath (referred to as gaspathcomponents) below a maximum temperature and prevent damage to thecomponent.

In some exemplary gaspath components, such as rotors and blades, amongothers, the active cooling takes the form of a film cooling process. Infilm cooling, a series of holes eject a stream of coolant, such as air,along a surface of the gaspath component being cooled. The stream ofcoolant simultaneously cools the exterior surface and provides a bufferzone prevent at least a portion of the high temperature gasses in thegaspath from contacting the gaspath component. Film cooling can beutilized in conjunction with other active cooling systems, or on it'sown to cool a gaspath component depending on the needs of the gaspathcomponent.

SUMMARY OF THE INVENTION

In one exemplary embodiment a component for a gas turbine engineincludes a body having at least one internal cooling cavity and aplurality of film cooling holes disposed along a first edge of the body,at least one of the film cooling holes including a metering sectiondefining an axis, and a diffuser section having a centerline, thecenterline of the diffuser section being offset from the axis of themetering section.

In another exemplary embodiment of the above described component for agas turbine engine the centerline of the diffuser section is offset fromthe axis of the metering section in an upstream direction.

In another exemplary embodiment of any of the above described componentsfor a gas turbine engine the centerline of the diffuser section isoffset from the axis of the metering section by at least 12.5% of thediameter of the metering section.

In another exemplary embodiment of any of the above described componentsfor a gas turbine engine the centerline of the diffuser section isoffset from the axis of the metering section by at least 25% of thediameter of the metering section.

In another exemplary embodiment of any of the above described componentsfor a gas turbine engine the centerline of the diffuser section isoffset from the axis of the metering section by approximately 25% of thediameter of the metering section.

In another exemplary embodiment of any of the above described componentsfor a gas turbine engine wherein each of the film cooling holes has ablowing ratio of approximately 1.0.

In another exemplary embodiment of any of the above described componentsfor a gas turbine engine the metering section is cylindrical and has acircular cross section normal to the axis.

In another exemplary embodiment of any of the above described componentsfor a gas turbine engine the centerline of the diffuser section and theaxis of the metering section are in parallel.

In another exemplary embodiment of any of the above described componentsfor a gas turbine engine the at least one film cooling hole is a 7-7-7film cooling hole.

In another exemplary embodiment of any of the above described componentsfor a gas turbine engine wherein the at least one film cooling hole is a10-10-10 film cooling hole.

In another exemplary embodiment of any of the above described componentsfor a gas turbine engine the upstream direction is a forward offsetdirection, relative to an expected fluid flow across an exterior surfaceof the body.

An exemplary method for manufacturing a film cooled article includesoffsetting a diffuser of at least one film cooling hole relative to ametering portion of the at least one film cooling hole.

In a further example of the above described exemplary method formanufacturing a film cooled article the metering portion is manufacturedin a first manufacturing step, and the diffuser section is manufacturedin a second manufacturing step distinct form the first manufacturingstep.

In a further example of any of the above described exemplary methods formanufacturing a film cooled article the metering portion and thediffuser portion are simultaneously manufactured.

In a further example of any of the above described exemplary methods formanufacturing a film cooled article offsetting the diffuser comprisingmanufacturing the diffuser such that a centerline of the diffuser is notcollinear with an axis defined by the metering portion.

A further example of any of the above described exemplary methods formanufacturing a film cooled article further includes maintaining thecenterline of the diffuser in parallel with the axis defined by themetering portion.

A further example of any of the above described exemplary methods formanufacturing a film cooled article further includes manufacturing thediffuser such that the centerline of the diffuser is skew relative tothe axis defined by the metering portion.

A further example of any of the above described exemplary methods formanufacturing a film cooled article further includes offsetting thediffuser upstream of the metering portion.

A further example of any of the above described exemplary methods formanufacturing a film cooled article further includes offsetting thecenterline of the diffuser section from the axis of the metering portionby at least 12.5% of the diameter of the metering section.

A further example of any of the above described exemplary methods formanufacturing a film cooled article further includes offsetting thecenterline of the diffuser section from the axis of the metering portionby at least 25% of the diameter of the metering section.

A further example of any of the above described exemplary methods formanufacturing a film cooled article further includes offsetting thecenterline of the diffuser section from the axis of the metering portionby approximately 25% of the diameter of the metering section.

These and other features of the present invention can be best understoodfrom the following specification and drawings, the following of which isa brief description.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 schematically illustrates a gas turbine engine including multiplegaspath components.

FIG. 2 schematically illustrates an exemplary gaspath componentincluding a series of film cooling holes.

FIG. 3 schematically illustrates a negative space of one exemplary filmcooling hole.

FIG. 4 schematically illustrates multiple specific arrangements of thenegative space illustrated in FIG. 3.

FIG. 5 schematically illustrates a surface view of multiple specificarrangements of a film cooling hole.

DETAILED DESCRIPTION OF AN EMBODIMENT

FIG. 1 schematically illustrates a gas turbine engine 20. The gasturbine engine 20 is disclosed herein as a two-spool turbofan thatgenerally incorporates a fan section 22, a compressor section 24, acombustor section 26 and a turbine section 28. Alternative engines mightinclude an augmentor section (not shown) among other systems orfeatures. The fan section 22 drives air along a bypass flow path B in abypass duct defined within a nacelle 15, while the compressor section 24drives air along a core flow path C for compression and communicationinto the combustor section 26 then expansion through the turbine section28. Although depicted as a two-spool turbofan gas turbine engine in thedisclosed non-limiting embodiment, it should be understood that theconcepts described herein are not limited to use with two-spoolturbofans as the teachings may be applied to other types of turbineengines including three-spool architectures.

The exemplary engine 20 generally includes a low speed spool 30 and ahigh speed spool 32 mounted for rotation about an engine centrallongitudinal axis A relative to an engine static structure 36 viaseveral bearing systems 38. It should be understood that various bearingsystems 38 at various locations may alternatively or additionally beprovided, and the location of bearing systems 38 may be varied asappropriate to the application.

The low speed spool 30 generally includes an inner shaft 40 thatinterconnects a fan 42, a first (or low) pressure compressor 44 and afirst (or low) pressure turbine 46. The inner shaft 40 is connected tothe fan 42 through a speed change mechanism, which in exemplary gasturbine engine 20 is illustrated as a geared architecture 48 to drivethe fan 42 at a lower speed than the low speed spool 30. The high speedspool 32 includes an outer shaft 50 that interconnects a second (orhigh) pressure compressor 52 and a second (or high) pressure turbine 54.A combustor 56 is arranged in exemplary gas turbine 20 between the highpressure compressor 52 and the high pressure turbine 54. A mid-turbineframe 57 of the engine static structure 36 is arranged generally betweenthe high pressure turbine 54 and the low pressure turbine 46. Themid-turbine frame 57 further supports bearing systems 38 in the turbinesection 28. The inner shaft 40 and the outer shaft 50 are concentric androtate via bearing systems 38 about the engine central longitudinal axisA which is collinear with their longitudinal axes.

The core airflow is compressed by the low pressure compressor 44 thenthe high pressure compressor 52, mixed and burned with fuel in thecombustor 56, then expanded over the high pressure turbine 54 and lowpressure turbine 46. The mid-turbine frame 57 includes airfoils 59 whichare in the core airflow path C. The turbines 46, 54 rotationally drivethe respective low speed spool 30 and high speed spool 32 in response tothe expansion. It will be appreciated that each of the positions of thefan section 22, compressor section 24, combustor section 26, turbinesection 28, and fan drive gear system 48 may be varied. For example,gear system 48 may be located aft of combustor section 26 or even aft ofturbine section 28, and fan section 22 may be positioned forward or aftof the location of gear system 48.

The engine 20 in one example is a high-bypass geared aircraft engine. Ina further example, the engine 20 bypass ratio is greater than about six(6), with an example embodiment being greater than about ten (10), thegeared architecture 48 is an epicyclic gear train, such as a planetarygear system or other gear system, with a gear reduction ratio of greaterthan about 2.3 and the low pressure turbine 46 has a pressure ratio thatis greater than about five. In one disclosed embodiment, the engine 20bypass ratio is greater than about ten (10:1), the fan diameter issignificantly larger than that of the low pressure compressor 44, andthe low pressure turbine 46 has a pressure ratio that is greater thanabout five (5:1). Low pressure turbine 46 pressure ratio is pressuremeasured prior to inlet of low pressure turbine 46 as related to thepressure at the outlet of the low pressure turbine 46 prior to anexhaust nozzle. The geared architecture 48 may be an epicycle geartrain, such as a planetary gear system or other gear system, with a gearreduction ratio of greater than about 2.3:1. It should be understood,however, that the above parameters are only exemplary of one embodimentof a geared architecture engine and that the present invention isapplicable to other gas turbine engines including direct driveturbofans.

A significant amount of thrust is provided by the bypass flow B due tothe high bypass ratio. The fan section 22 of the engine 20 is designedfor a particular flight condition—typically cruise at about 0.8 Mach andabout 35,000 feet (10668 meters). The flight condition of 0.8 Mach and35,000 ft (10668 m), with the engine at its best fuel consumption—alsoknown as “bucket cruise Thrust Specific Fuel Consumption (‘TSFCT’)”—isthe industry standard parameter of lbm of fuel being burned divided bylbf of thrust the engine produces at that minimum point. “Low fanpressure ratio” is the pressure ratio across the fan blade alone,without a Fan Exit Guide Vane (“FEGV”) system. The low fan pressureratio as disclosed herein according to one non-limiting embodiment isless than about 1.45. “Low corrected fan tip speed” is the actual fantip speed in ft/sec divided by an industry standard temperaturecorrection of [(Tram ° R)/(518.7° R)]{circle around ( )}0.5. The “Lowcorrected fan tip speed” as disclosed herein according to onenon-limiting embodiment is less than about 1150 ft/second (350.5 m/s).

In order to compensate for the extreme temperatures generated by thecombustion, gaspath components, such as the blades and stators at aninlet of the turbine section 28 include active cooling systems. Amongother cooling techniques the active cooling systems utilize a filmcooling technique.

With continued reference to FIG. 1, FIG. 2 illustrates an exemplary filmcooled gaspath component 100. The exemplary film cooled gaspathcomponent 100 is a stator, however one of skill in the art having thebenefit of this disclosure will understand that the shaped film coolingholes described herein can be utilized in any type of film cooledcomponent, and are not limited to stators.

The film cooled component 100 includes a radially inward platformsection 110, a radially outward platform section 120, and a vane portion130 extending between the platforms 110, 120. The vane portion 130includes a leading edge 132 positioned at a fore most edge of the vaneportion 130, relative to an expected direction of fluid flow through theengine. Similarly, the vane portion 130 includes a trailing edge 134positioned at an aft most edge of the vane portion 130, relative to anexpected direction of fluid flow through the engine.

Along the leading edge 132 are multiple rows of film cooling holes 136.The film cooling holes 136 are connected to an internal plenum thatreceives a cooling fluid from either the radially outward platform 120or the radially inward platform 110. The cooling fluid is pressurizedand is forced out of the film cooling hole along the surface of the vaneportion 130. The cooling fluid forms a layer of fluid, or a film, thatadheres to the vane portion 130 and simultaneous cools the vane portion130 and provides a buffer against hot gasses within the gaspathcontacting the vane portion 130.

With continued reference to FIGS. 1 and 2, FIG. 3 schematicallyillustrates a negative space of one exemplary film cooling hole 200. Thefilm cooling hole 200 is a shaped film cooling holes. Shaped filmcooling generally consist of a metering section 210 through the materialof the gaspath component and a diffuser 220 to spread coolant over thesurface of the gaspath component. In order to spread the coolant thediffuser 220 is angled outward from the metering section 210, andexpands the coolant. In one example the diffuser 220 is angled at 7degrees in the forward and lateral directions, and is referred to as a7-7-7 film cooling hole. In an alternate example, the diffuser 220 isangled at 10 degrees in the forward and lateral directions and isreferred to as a 10-10-10 film cooling hole. The intentional offsetbetween the diffuser 220 and the metering section 210 is applicable toboth 7-7-7 holes and 10-10-10 holes, as well as any number of other filmcooling hole styles, as will be understood by one of skill in the art.

These metering section 210 and the diffuser 220 are typically createdusing distinct machining actions. In some examples the holes are createdusing electrical discharge machining, although any alternative machiningprocess can be used to similar effect. Conventional film cooling holesare designed such that a centerline 222 of the diffuser section, and anaxis 212 of the metering section 210 are collinear. The centerline 222of the diffuser 220 is defined as a line drawn from a midpoint of theopening intersecting with the metering section 210 to a midpoint of theopening in the exterior of the gas path component 100 (see FIG. 1).

In the illustrated example, the metering section 210 is generallycylindrical with a circular cross section parallel to an axis 212defined by the cylinder. In alternative examples, the metering section210 can be formed with alternative cross sectional shapes, such asregular polygons, and function in a similar manner. The metering section210 provides a through hole to the pressurized internal cavity andallows cooling fluid to be passed from the internal cavity to anexterior surface of the gas path component 100. In some examples, thepressurized internal cavity is an impingement cavity

The diffuser 220 is an angled hole with a wider opening 224 at an outletend on the surface of the gas path component and a narrower opening 226,approximately the same size as the metering section 210 cross sectioninterior to the gas path component. By aligning the axis 212 of themetering section 220 with a centerline 222 of the diffuser 220, thediffuser 220 is able to expand and direct the cooling gas emitted fromthe metering section 220 and thereby enhance the film cooling layer.

Since the metering section 210 and the diffuser 220 are machined intothe gas path component via separate machining actions, it is possible toinclude an intentional offset between the axis 212 of the meteringsection 210 and the centerline 222 of the diffuser 220. With continuedreference to FIG. 3, and with like numerals indicating like elements,FIGS. 4 and 5 schematically illustrate exemplary intentional offsets.Included in the illustration of FIG. 5 is a key illustrating the terms“fore”, “aft”, and “left” as they are applied to a given film coolinghole 200. Illustration A shows a film cooling hole 200 where thediffuser 220 and the metering section 210 are not offset. Illustration Bshows a diffuser 220 that is offset left by one quarter of the diameterof the circular cross section of the metering portion 210. IllustrationC shows a diffuser 220 that is offset forward by one quarter of thediameter of the circular cross section of the metering portion 210.Illustration D shows a diffuser 220 that is offset aftward by onequarter of the diameter of the metering portion 210. In some examples,the intentional offset will result in the centerline 222 and the axis210 being parallel, but not collinear. In other examples, the offset caninclude a rotation of the diffuser section, and the centerline 222 andthe axis 210 can be skew. While referred to herein by their relationshipto the diameter of the circular cross section of the film cooling hole,one of skill in the art will understand that in the alternative examplesusing differently shaped metering sections, the diameter referred to isa hydraulic diameter.

In a similar vein, FIG. 5 illustrates view of five different offsets atthe surface of the gaspath component, with view 410 corresponding toillustration C of FIG. 4, view 420 corresponding to illustration B ofFIGS. 4, and 430 corresponding to illustration D of FIG. 4. It is alsorecognized that any of the offsets described above can be combined withanother offset. By way of example, view 415 is a combination of theoffsets of views 410 and 420, alternately referred to as a fore-leftoffset. In another example, view 425 is a combination of views 420 and430, alternately referred to as an aft-left offset. When including anintentional offset, the diffuser 220 is not aligned with the crosssection of the metering section 210. As a result, the flow of coolantthrough the metering section 210 into the diffuser 220, and thuscreating the film on the gaspath component, is restricted to the shadedregion 402.

Further, while illustrated in the exemplary embodiments as 90 degreeincrements for the offsets, one of skill in the art will understand thatan offset can be made according to any known increment and achieve adesired purpose, with the magnitude of the offset and the angle of theoffset being determined by the specific needs of the given application.

Offsetting the diffuser 220 from the metering section 21 affects thedisbursement of the cooling fluid along the surface of the gas pathcomponent including the film cooling hole 200, and has a correspondingeffect on the efficacy of the film cooling.

In some examples, such as the illustrated aft shifts of FIGS. 4 and 5,ideal cooling is achieved by shifting the diffuser 220 upstream relativeto an expected fluid flow through the gas path of the turbine engine inwhich the gas path component is located. Shifting the diffuser 220upstream increases the cooling capabilities of the film cooling system.In yet further examples, the diffuser 220 is shifted upstream by onequarter (25%) of the diameter of the metering section 210. In otherexamples, ideal cooling is achieved by shifting the diffuser 220upstream by one eighth (12.5%) of the diameter of the metering section210. In other examples, the diffuser 220 is shifted by an amount withinthe range of one eight to one quarter of the diameter of the meteringsection 210. In further alternative examples the diffuser 210 can beshifted upstream by any suitable amount, and the shifting is not limitedto the range of one eight to one quarter of the diameter of the meteringsection 210.

Another factor that impacts the effectiveness of the cooling provided byany given film cooling hole is the blowing ratio of the cooling hole.The blowing ratio is a number determined by ρ_(c)U_(c)ρ_(∞)U_(∞), whereρ_(c) is the density of the cooling fluid, U_(∞)is the velocity of thecooling fluid passing through the coolant hole, ρ_(∞), is the density ofthe fluid in the gaspath, and U_(∞)is the velocity of the fluid in thegaspath. In some examples, the film cooling provided is most effectivewhen the blowing ratio is 1.0, with the cooling effectiveness decreasingthe farther the film gest from the originating film cooling hole.

It is further understood that any of the above described concepts can beused alone or in combination with any or all of the other abovedescribed concepts. Although an embodiment of this invention has beendisclosed, a worker of ordinary skill in this art would recognize thatcertain modifications would come within the scope of this invention. Forthat reason, the following claims should be studied to determine thetrue scope and content of this invention.

1. A component for a gas turbine engine comprising: a body having atleast one internal cooling cavity; and a plurality of film cooling holesdisposed along a first edge of said body, at least one of the filmcooling holes including a metering section defining an axis, and adiffuser section having a centerline, the centerline of the diffusersection being offset from the axis of the metering section.
 2. Thecomponent of claim 1, wherein the centerline of the diffuser section isoffset from the axis of the metering section in an upstream direction.3. The component of claim 2, wherein the centerline of the diffusersection is offset from the axis of the metering section by at least12.5% of the metering section.
 4. The component of claim 3, wherein thecenterline of the diffuser section is offset from the axis of themetering section by at least 25% of the diameter of the meteringsection.
 5. The component of claim 4, wherein the centerline of thediffuser section is offset from the axis of the metering section byapproximately 25% of the diameter of the metering section.
 6. Thecomponent of claim 1, wherein each of the film cooling holes has ablowing ratio of approximately 1.0.
 7. The component of claim 1, whereinthe metering section is cylindrical and has a circular cross sectionnormal to the axis.
 8. The component of claim 1, wherein the centerlineof the diffuser section and the axis of the metering section are inparallel.
 9. The component of claim 1, wherein the at least one filmcooling hole is a 7-7-7 film cooling hole.
 10. The component of claim 1,wherein the at least one film cooling hole is a 10-10-10 film coolinghole.
 11. The component of claim 1, wherein the upstream direction is aforward offset direction, relative to an expected fluid flow across anexterior surface of the body.
 12. A method for manufacturing a filmcooled article comprising: offsetting a diffuser of at least one filmcooling hole relative to a metering portion of the at least one filmcooling hole.
 13. The method of claim 12, wherein said metering portionis manufactured in a first manufacturing step, and said diffuser sectionis manufactured in a second manufacturing step distinct form said firstmanufacturing step.
 14. The method of claim 12, wherein said meteringportion and said diffuser portion are simultaneously manufactured. 15.The method of claim 12, wherein offsetting the diffuser comprisingmanufacturing the diffuser such that a centerline of the diffuser is notcollinear with an axis defined by the metering portion.
 16. The methodof claim 15, further comprising maintaining the centerline of thediffuser in parallel with the axis defined by the metering portion. 17.The method of claim 15, further comprising manufacturing the diffusersuch that the centerline of the diffuser is skew relative to the axisdefined by the metering portion.
 18. The method of claim 15, furthercomprising offsetting the diffuser upstream of the metering portion. 19.The method of claim 18, further comprising offsetting the centerline ofthe diffuser section from the axis of the metering portion by at least12.5% of the diameter of the metering section.
 20. The method of claim19, further comprising offsetting the centerline of the diffuser sectionfrom the axis of the metering portion by at least 25% of the diameter ofthe metering section.
 21. The method of claim 20, further comprisingoffsetting the centerline of the diffuser section from the axis of themetering portion by approximately 25% of the diameter of the meteringsection.